I know that in string theory it is believed that there are extra dimensions, and parallel universes, and that every event that can take place in more than one way causes our universe to split into multiple parallel universes. Well I was thinking that as things in one part of space cannot be effected by the events of another part of space until there has been time for the light from that other part of space to reach it that the split of the universe associated with any event happens only at the speed of light. So the way the universe splits from events may depend on space as well as time.

String theory does not predict, or need, parallel universes or the kind of splitting that Everett proposed. These things are optional extras which appear in some proposals based on string theory, typically also on M-theory, which is a generalisation of string theory.

In particular Everett proposed the relentless splitting into parallel universes as a way to overcome a technical problem with quantum mechanics, sometimes referred to as the collapse of the wave function. By splitting possibilities into parallel universes, the wave function need never collapse. However some consequences such as the theory's utterly gross violation of the law of conservation of energy have never been successfully explained: if quantum events throughout the universe are continuously creating untold billions of parallel universes every second, where does all that energy come from? I find it easier to believe that we don't understand quantum mechanics.

M-theory is a little less, um... hard to swallow. It allows a variety of branes (universes having arbitrary numbers of dimensions up to I think 10) to float around in an 11-dimensional "multiverse" and create new branes at a more leisurely rate. The ways that this might happen are poorly understood. Some theories suggest that when a black hole forms it creates a new brane. Since a black hole is a powerful curvature of Minkowski spacetime so that one dimension of space becomes timelike and time becomes spacelike, yes space is as important as time in any such scenario.

It seems that scientists/ theorist will always do what they do best, argue. Their advancements have been pretty cool though. I would have loved to have been at this lecture. I wonder if there will ever come a day when we learn how to connect with other dimensions, or if we would regret it if we did. Seems like all this lifetime is going to have is a bunch of questions on the matter.